WO 97/50132 discloses a radiation-emitting optoelectronic component in which at least some of the radiation emitted by an active layer of the optoelectronic component is converted by a luminescence conversion layer to longer wavelengths. In this manner, mixed-color or white light can be produced, e.g., with a radiation-emitting active zone which emits ultraviolet or blue light. By the luminescence conversion layer, ultraviolet or blue light is thereby generally converted into light of a longer wavelength, in particular into light of a complementary color such as yellow, for example, to generate white light.
In the case of that type of generation of white light by luminescence conversion, the visual impression of the optoelectronic component in the switched-off state is often unsatisfactory. The reason for this is that in a bright environment even when the optoelectronic component is in the switched-off state the luminescence conversion layer is excited to emit yellow light which, however, in contrast to the operating state is not mixed with emitted ultraviolet or blue light to produce white light. As a consequence, the surface of the optoelectronic component in the switched-off state has, in the regions provided with the luminescence conversion layer, the color of the longer wavelength generated by luminescence conversion, e.g., yellow, which is often perceived by observers as unattractive. This is the case in particular with comparatively large-scale illumination units which are based, e.g., upon organic light-emitting diodes (OLEDs), but also with LEDs or LED modules having one or a plurality of radiation-emitting semiconductor chips.
To reduce the yellow color impression of the luminescence conversion layer when a radiation-emitting, optoelectronic semiconductor chip is in the switched-off state, it is proposed in DE 10 2006 051 746 A1 to dispose a light-scattering layer, which contains, e.g., scattering particles, above the luminescence conversion layer.
In the case of radiation-emitting, optoelectronic components which have that type of layer sequence consisting of a luminescence conversion layer and a scattering layer, the resulting color impression in the switched-on and/or switched-off state depends in particular upon the thicknesses of the luminescence conversion layer and the scattering layer and upon the properties of the boundary surfaces of these layers. In particular, deviations in the layer thicknesses of the luminescence conversion layer and/or the scattering layer can lead to a deviation in the color impression of the optoelectronic component from a desired reference value.
It could therefore be helpful to provide a process of producing a layer composite having a luminescence conversion layer and a scattering layer, which renders it possible to produce the layers of the layer composite with a high degree of precision in relation to the layer thicknesses and dimensions thereof, wherein the production outlay is relatively small.